Field of the Invention. The present invention relates to internal combustion engines. More specifically, the present invention relates to reducing or eliminating the combination of combustion gases and oil in the crankcase of an internal combustion engine.
Background Information. In an internal combustion engine, providing a piston ring seal between the pistons and the surrounding cylinder walls that completely seals off the combustion chambers from the crank case of the engine has yet to be done. A certain small quantity of combustion gases, or blow-by, flows past the piston ring down into the crankcase of the engine. In order to avoid a high overpressure in the crankcase at least partially due to the blow-by gases, the crankcase must be ventilated. The more effective the ventilation is, the lower the overpressure in the crank case and, therefore, the lower the engine pumping losses become. On the other hand, if there is a loss in crankcase pressure, oil consumption can increase due to oil vapor carried by the blow-by being evacuated by the positive crankcase ventilation system.
In modern engines, closed crankcase ventilation is used in order to minimize environmental effects. Normally, any blow-by gases and water vapor present are allowed to enter the crankcase where they are mixed vigorously with and become trapped within the oil droplets suspended in the crankcase. Afterwards, the oil droplets are led out from the crankcase via a hose to the inlet manifold of the engine before the throttle, where they are mixed with the intake air. In order to separate oil out of the oil mist unavoidably mixed with the blow-by gases, different types of filters and oil traps are used in the crankcase ventilation. Typically, crankcase ventilation systems separate oil from blow-by after they have been mixed together. Also, overpressure in the crankcase that increases with power demand is minimized by adding a pressure regulator.
Accordingly, there is a need for an internal combustion engine that reduces or eliminates overpressure in the crankcase that occurs with an increase in power demand. Further, there is a need for an internal combustion engine that minimizes or avoids the mixing of blow-by gases and oil.
The present invention includes a cylinder block with at least one cylinder barrel, a cylinder head with at least one inlet channel and exhaust channel with associated inlet and output valves for a combustion chamber. The combustion chamber is located above a piston moveable in the cylinder barrel. Below the piston is a crank case wherein lubricating oil is found. The piston is shaped with at least two peripheral grooves situated at a distance from each other, each having its own piston ring. A piston collection chamber is contained between the rings.
The present invention provides a means of avoiding the mixing of blow-by and oil. This is achieved by evacuating unburned blow-by mixture and combustion gases directly into an expansion chamber via an evacuation port in the cylinder wall, instead of letting them expand in the crankcase. Therefore, the gases do not mix intimately with the oil in the crankcase, facilitating the separation and oil trap operation. When expanding, the gases lose much of the flow rate energy that could otherwise allow them to carry and mix with oil droplets present in or near the evacuation port.
Even with a pressure regulator provided, engines are inclined to have a much higher pressure in the crankcase than in the combustion chamber during intake stroke. This pressure tends to press both the oil film on the cylinder wall and the oil mist in the crankcase past the oil scraper ring of the piston and into the combustion chamber of the engine. In order to prevent to as best possible this oil flow to the combustion chamber, the ring tension must be high for the oil scraper ring. The oil scraper ring is the component that causes the greatest internal friction in the engine.
The oil that penetrates into the combustion chamber of the engine does not just cause pollution in the engine exhaust gases, with consequential strain on the catalyzer. It also lowers the octane number of the fuel. In modern engines with knock sensors and automatic ignition advance, this leads to a retarding of the ignition with consequential increased fuel consumption. Further, engine oil consumption and the costs of replacing used oil are directly dependent on the amount of oil that penetrates into the combustion chamber due to the pressure difference between the crank case and the cylinder space above the piston.
Oil combustion also contributes to deposits in and around the piston rings. These deposits can interfere with the proper operation of the rings, and may eventually immobilize the rings, along with deteriorating their function.
The present invention provides an engine wherein the pressure difference between the engine crankcase and its air intake is maintained as low as possible. This pressure difference forces the lubricating oil past the piston rings and into the combustion chamber during the intake stroke of the engine. In other words, the pressure due to the pressure difference between the crankcase and the air intake during all operating conditions is lowered, thereby minimizing oil consumption, as well as pumping, windage and friction losses. Further, the present invention eliminates the need for a colder oil trap for condensing and recovering oil, and also prevents the system from freezing.
In the present invention, the cylinder block has been designed with an evacuation port for each cylinder. The channel opening into the cylinder barrel forms a communicating connection between the cylinder barrel and the intake channel, preferably in close proximity to an engine coolant passage. The evacuation channel outlet and the piston are adapted to each other such that the piston holds the evacuation channel open during movement of the piston from its top dead center to a position at a predetermined distance from top dead center (TDC), thereby maintaining the connection between the crankcase and the intake channel. Thereafter, the piston breaks the connection between the evacuation channel and the crankcase by its continued movement down to bottom dead center (BDC).
Also, the cylinder outlet port of the evacuation channel is adapted to provide communication with the piston collection chamber during the movement of the piston from TDC to a position at a predetermined distance from TDC. However, since the crankcase pressure in previously known engines is relatively high, and the volume and the rate of blow-by gases intended to flow into the evacuation channel is relatively high, the flow resistance in the evacuation channel becomes relatively high.
An oil trap is arranged in the evacuation channel to prevent oil particles in the blow-by gases flowing into the evacuation channel from reaching the intake channel and burning in the combustion chamber. However, since the flow rate of the blow-by gases in the evacuation channel is relatively high, it is difficult to prevent all oil particles from reaching the inlet channel.
The present invention provides an engine wherein the pressure pulses and the flow rate of blow-by gases in the evacuation channel is lower than in previously known engines, minimizing the flow velocity of the blow-by gases and preventing oil particles from reaching the inlet channel, while evacuating blow-by to the air inlet.
This is achieved according to the invention by providing the engine with an expansion chamber commonly connected to each cylinder via an individual evacuation port. The port opens out into the respective cylinder barrel. The expansion chamber forms a communicating connection between the cylinder barrel and the inlet channel via the evacuation port and an evacuation channel. The evacuation channel opens out into at least one inlet channel or inlet manifold, and the evacuation port and piston are so adapted to each other that the piston holds the evacuation port open, thereby maintaining the connection between the crankcase and the inlet channel during the piston""s movement from its top dead center to a position at a predetermined distance from the top dead center. Thereafter, the piston breaks the connection of the evacuation port with the crankcase during its continued movement down to bottom dead center. The collection chamber is connected to the evacuation port when the piston is near the bottom dead center. This allows better pressure equalization between the inlet channel or manifold and the crankcase, while providing necessary communication and reducing the amount of oil splashes which could reach the port.
By providing a chamber having a large cross section between the evacuation port in the cylinder barrel and the inlet channel, blow-by gases coming from the evacuation port can expand, thereby reducing the pressure pulse magnitude and slowing down the flow of blow-by to a less turbulent state, resulting in more oil particles settling and being trapped. This expansion chamber is also provided with a return for permitting the oil to return to the crankcase from a less turbulent area of the chamber.
In a preferred embodiment, a cyclone tube is arranged in the expansion chamber in proximity to the evacuation ports. The cyclone tube, which can be double open ended, causes the blow-by gases to circulate so that oil particles in the blow-by are centrifugally forced into contact with a surface. Also, baffles can be arranged in the expansion chamber for increasing the contact area for the oil to cling to, and for reducing the pressure and speed of the circulating blow-by gas. By maintaining a negative pressure, water vapor will vaporize easily while oil droplets will cling to the cyclone surface due to its higher viscosity.
The piston is a conventional cylindrical piston that, according to the invention, can be provided with a shield on the side facing the opening of the evacuation port, which forms a screening-off towards the opening of the evacuation port thereby limiting the intrusion of oil splashes. The screen has a greater clearance towards the cylinder barrel wall than the piston cylinder so that the crank case, via the gap formed through the greater clearance, and the evacuation port are joined with the inlet channel, via the expansion chamber and the evacuation channel during a predetermined part of the path of movement of the piston.
Preferably, each piston has a collection chamber between the piston ring grooves for collecting unburned fuel-air mixture and combustion gases that pass the upper piston ring. The cylinder preferably has an evacuation port so orientated in relation to the collecting chamber that, after a predetermined movement of the piston from its top or bottom dead center portion, a communicating connection is established between the piston collection chamber and the inlet channel via the evacuation channel and the expansion chamber. In this way, unburned fuel-air mixture and combustion gases are prevented from reaching the crankcase. Instead they are ventilated out through the evacuation channel into the expansion chamber. They then flow to the inlet channel due to an overpressure that occurs in the collection chamber, while an underpressure occurs in the cylinder evacuation channel. Otherwise, unburned fuel-air mixture trapped under the first piston ring would flow back into the combustion chamber during the expansion stroke as soon as the cylinder pressure fell below the pressure of the mixture. However, this would occur too late for the mixture to be able to be burnt. To reduce pressure due to the volume of unburned fuel-air mixture and combustion gases in the collection chamber, the piston can be provided with a space, such as plurality of bores, communicating with the collection chambers In doing so, the total volume of the collection chamber is increased, leading to a reduction in pressure of the gases taken up in the collection chamber.